Plate spring or retaining grid for a bunch cylindrical elements engaged in a heat exchange process

ABSTRACT

Grid for the retaining or laterally supporting of primarily nuclear fuel rods, comprising plate springs that exert a retaining force remaining constant, irrespective of the degree of compression. A spring may be spotwelded to the grid, snapped into place in a hole in the grid wall, or both.

United States Patent Piepers et al.

[ Dec. 30, 1975 [54] PLATE SPRING OR RETAINING GRID FOR 3,646,994 3/1972Pie ers et al. 176/78 A BUNCH CYLINDRIC L ELEMENTS 3,679,546 7/1972Nluellner et al. 176/78 ENGAGED IN A H EXCHANGE 3,769,159 10/1973 Zmn eta1. 176/78 PROCESS FOREIGN PATENTS OR APPLICATIONS [75] lnvemors FGerhard E 346,144 4 1931 United Kingdom 267/164 1-1e1loo; LeonardHendrik Vons, 631,061 11/1961 Canada 267/164 Bergen, both of Netherlands[73] Assignee: g i :ederland The Primary Examiner-Verlin R. Pendegrassague et er an S Attorney, Agent, or FirmCushman, Darby & [22] Filed:June 27, 1973 Cushman [21] Appl. No.: 374,065

' 57 ABSTRACT [30] Foreign Application Priority Data July 10, 1972Germany 2233904 Grid for the retaining or laterally supporting ofprimarily nuclear fuel rods, comprising plate springs that [52] US.CL... 176/78; 165/69 exert a retaining force remaining constant,irrespec- [51] Int. Cl. G2lc 3/18; G210 3/34 tive of the degree ofcompression. A spring may be [58] Field of Search 176/78; 267/164;165/69 spotwelded to the grid, snapped into place in a hole in the gridwall, or both.

[56] References Cited UNITED STATES PATENTS 3 Claims, 10 Drawing Figures3,379,617 4/1968 Andrews et a1 176/78 0T s 2 s K 95 1, Z 96 98 g 92 Z 90a1 99 27 III-11- 4 m 4 6 15 e1 93 -s1 US. Patent Dec.30, 1975 Sheet10f83,929,569

Fig.1

Sheet 3 of 8 III/ll amt Dec. 30, 1975 Sheet4 0f8 3,92 5

., amt Dec.30, 1975 SheetS 0f8 392956 Fig. 6

US. Patent Dec. 30, 1975 Sheet 6 of8 3329 569 Fig. 8

Dec. 30, 1975 Sheet 7 of 8 3,9256

. atem Fig.9

PLATE SPRING OR RETAINING GRID FOR A BUNCH CYLINDRICAL ELEMENTS ENGAGEDIN A HEAT EXCHANGE PROCESS The invention relates to a retaining grid orsupporting grid for laterally supporting a bunch of cylindrical elementsengaged in a heat exchange process, the supporting grid being made up ofstrip material in such a way that a plurality of compartments is formed.

One of the objects of the invention is to indicate a structure for agrid of this kind in which a plate spring is introduced at least at oneposition into aside wall of a compartment. The plate spring extends intwo directions and, when released, shows an arched form in one directionin its principal middle part, whilst the outer ends of the plate springare in rigid connection with fixing points of the said side wall,between which fixing points and a span of distance near at least one endof the plate spring a smaller section is similarly arched in the form ofa plate spring.

The said cylindrical elements may consist, for instance, of rods or barsof fissile or breeding material which are introduced into the core of anuclear reactor. The same set-up, however, may also be used for a heatexchanger. In that case the cylindrical compartments consist of pipesaround which there is a flow of media to be cooled or heated.

Lastly, it is also possible to use a set-up mounted inside thecylindrical elements.

The said plate springs have a non-linear spring characteristic. Thepressure increase with the degree of compression according to thedimensional conditions ruling at any moment, but remains constant ordecreases within a certain range. Consequently, it is possible withincertain limits to apply an equal pressure to all the cylindricalelements, independently of manufacturing and assembling tolerances andtemperature effects. This is of particular importance in cases where thepressure and spring tensions may not exceed certain permissible maximumvalues. It is not necessary to give the spring a symmetrical shaping inthe longitudinal direction. Thus, it is quite possible to use a platespring having only one curved section in connection with the archedspan. In this embodiment the plate spring is shorter, which isadvantageous to the flow of medium around it.

his a further object of the invention to use a plate spring having onlyon one side a curved section in connection with the arched span. Theadvantage of this form of spring is that the spring becomes shorter andcan therefore be manufactured in a more simple and hence less expensivemanner.

According to a further embodiment of the invention a plate spring isused which shows at least on one side of the large archlike convexitysmaller convex spring portions which are outwardly curved towards theopposite side of the large convexity. In this way a form of spring isobtained which is characterized in that it can be produced in a veryeasy manner if these small convexities of the spring are formed at bothends. By giving the plate spring a suitable shaping it is now possiblewith these slight spring convexities to make the plate spring rest inholes provided in the wall of the grid. With suitable shaping it is evenpossible in this embodiment to bring about a so-called snap connection.In that case the plate spring is brought into position by being pushedthrough the apertures until the two convexities snap through thisaperture, whereupon the spring is fixed in the grid. For greatersecurity it is always possible to fix the ends of this spring throughthe grid additionally by means of spot welds. Should such a spot weldbecome detached, this spring is still unable to move out of the grid asit is kept locked in position by the snap joint.

The same holes in the grid wall which are used for fixing the platespring may also be utilized for fixing the rod holder in the same way.This rod holder, which is situated in the other compartment of the grid,serves to provide a firm point of support for the fissile rod by meansof a few projecting parts.

According to a further variant of the invention the springs used consistof an assembly of two or more springs mounted one above the other. Inthe case where two springs are used, these two springs are connected atleast to each others ends. The assembly of plate springs formed in thisway is connected at its ends to the grid by means of so-called backingstrips (rod holders). The advantage of this is that each springindividually shows a lower stress level than a replacement spring whosetotal length corresponds to the sum of the thickness of the individualsprings stacked upon each other. This lowered stress level is ofparticular importance because the degree of stress relaxation is afunction also of the magnitude of this stress level. By the use of thisassembly of composite springs it is possible to keep the stressrelexation under control in such a manner that the spring tension can bemaintained for a much longer time than was formerly the case. The resultis thus achieved that, in spite of the often very high workingtemperature, springs made in this way can perform their function in areliable manner for a long period.

Typical embodiments of the invention will be elucidated below byreference to the accompanying drawmgs:

FIG. 1: shows these spring characteristics.

FIG. 2; shows a longitudinal section II-II taken through the retainninggrid according to FIG. 4.

FIG. 3: represents a longitudinal section III III taken through theretaining grid according to FIG. 4. FIG. 4 gives a top plan view of theretaining grid.

FIG. 5: gives a top plan view of a non-symmetrical plate spring.

FIG. 6: is a front elevation of a cross-shaped rodshielding element.

FIG. 7: gives a side view of a non-symmetrical plate spring according toFIG. 5.

FIG. 8: shows, in an elevation according to VIII, a rod holder as usedin FIG. 9.

FIG. 9: discloses a vertical cross-section of a grid element in whichthe plate springs used show an amended form of construction.

FIG. 10: shows a side elevation of a doubly constructed non-symmetricalspring.

FIG. 1 shows the spring characteristics of plate spring of the kinddescribed.

The force K by which the plate is compressed in plotted along thevertical axis (see also FIG. 3).

The spring deformation f is represented by the horizontal axes. Thisspring deformation is measured in the middle 27 of the plate spring (seeFIG. 3).

The characteristics b and c in particular are of importance for thepurpose concerned here. Characteristic b shows a trend which ensures aconstant resiliency K between the limits d and e.

Characteristic b shows that it is also possible to make the resiliency Kdiminish according as the deformation increases. Springs with thischaracteristic as well as springs with characteristic b are suitable forintercepting the vibration of pipes or fuel rods. Such vibrations, whichmay be due to variations of pressure in the cooling medium, havehitherto frequently been a source of difficulty, as they are liable tocause fatigue fractures.

FIG. 4 shows, in a top plan view of a supporting grid 1, how a pluralityof rods 2 of fissile material are supported in this grid. The gridconsists of a plurality of strips 3, 4, 5 and 6 which are permanentlyconnected with each other at points 14, 15, 16 and 17, at whichintersecting strips interlock. In this .way a plurality of gridcompartments 7 is formed. For one of these sections the figure shows indetail how these rods 2 of fissile material are supported by a platespring 8 together with a rod holder having two bends 78 and 79 each ofwhich shows a protrusion 81, 82.

FIG. 3 shows, in a longitudinal section of the element of fissilematerial depicted in FIG. 4, how the plate springs used are shaped.According to FIG. 3 each plate spring shows an arched middle part whichmerges at its two ends into smaller plate spring parts 16 with anarching similar to that of the middle part 15.

At points 23 each end of the plate spring is rigidly fixed, e.g. bymeans of spot welds, to a side wall portion 5 of a compartment 7.

For the sake of clarity this is again shown in FIG. 3 in a longitudinalsection III III of the grid. It can furthermore be seen from the figurethat in the middle of the larger wall portion a protrusion 27 isprovided which is adjacent to the adjoining surface of the fissile rod2.

FIGS. 5 and 7 show a modified form in which a plate spring is shapednon-symmetrically with only one arched part.

If a rectangular set-up of the fissile rods is to be provided, the FIG.4 construction offers a simple and inexpensive mode of solution.According to FIG. 4. vertical strips 5 and 6 are connected by means ofsoldered or plasma-welded joints 14, 15, 16 and 17.

The plate springs 8 are fixed to the transverse strips 5 and 7respectively. These springs may be of the kind shown as spring 8 in FIG.2 or as springs in FIGS. 5 and 7.

Rod holders 76 and 77 give the fissile rod 2 a firm hold at points and46. FIG. 6 gives a top plan view of a rod holder 77. The curved clamps81 and 82 provide a firm hold. These clamps are the opposite ends of thecross-beam or strip of the cross-shaped part 77. The longitudinal strip85 is used for spot welds at points 86 and 87.

FIG. 2 is a front elevation of the plate spring 8 used in FIG. 3. Itdistinctly shows the positions 23 at which a spot weld has been made.

FIG. 9 shows in common with FIG. 3 a vertical crosssection of the grid,in which, however, a variant upon the letter figure is depicted. In thisembodiment two apertures 90 and 91 respectively are provided in the gridwalls 6 and 5 respectively. Since there are corresponding apertures 92and 93 respectively in the backing strip or rod holder 95, the platespring portions 96 and 97 which are bent over with small archings can bepushed through these apertures. During this action the spring 25 issupported by its end 98, bent over practically at right angles, in theedges 99 of the apertures. Although this is not shown in FIG. 9, thisconstruction can without difficulty be made in such a way that when theplate spring is pushed through apertures 90 and 91 a snap effect isbrought about, so that the spring is not only fixed in the apertures butcan as it were be locked in them.

FIG. 8 shows the view according to VIII on the rear side of theretaining plate 95. This plate is provided with bent-over edges 100 and101 by means of which the retaining plate is fixed upon the edges 102and 103 of apertures 92 and 93. As shown in FIG. 8, spot welds mayfurthermore be provided at the positions 23.

In FIG. 10 a construction is depicted partly in crosssection and partlyin side elevation, in which a spring 104 and a spring 105 aresuperimposed upon each other and fixed by means of spot welds 106 and107. If desired, a few other spot welds may be provided over the lengthof the spring, for example at 108. Spring 105 has for the sake ofclarity been given a different shade of colour from spring 104. FromFIG. 10 it can also be seen that the retaining plate 109 is in this caseprovided with two protrusions 110 and 111 which pass through apertures112 and 113 so as to come into contact with the underside of 105, wherethey are fixed with the same spot weld by means of which the springportions themselves are joined to each other.

We claim:

1. A supporting grid for supporting a plurality of elements engaged in aheat exchange process against sideways shifting comprising: a pluralityof grid strips connected together to form the sidewalls of a pluralityof compartments having parallel axes; a plate spring extendinglongitudinally in each compartment, said plate spring having acontinuous surface facing the sidewall of the respective compartment,said spring having a central arch-like bend projecting toward the centerof the respective compartment for engaging an element therein and havingat each end of the arch-like bend a smaller bend facing in the oppositedirection, said spring further having straight end portions which engagethe sidewall of the respective sidewall, each end portion extendinglongitudinally outwardly from the respective smaller bend so that thesurface of the end portion engaging the sidewall is part of saidcontinuous surface, each of said smaller bends projecting through I anaperture in the adjacent sidewall and engaging only that edge of therespective aperture which is adjacent the straight end portions of theplate spring to thereby fasten said plate spring to said adjacentsidewall; and an element holder in each compartment engaging thesidewall opposite the respective plate spring and having a portionprojecting toward the center of the compartment for engaging an elementtherein on the opposite side from the respective plate spring.

2. A grid as in claim 1 wherein said element holder includes a plateportion engaging the compartment sidewall, said plate portion beingprovided with two apertures each of which coincides with one of saidapertures in the compartment sidewall, an edge of each aperture in theplate portion being bent into a lip which grasps the edge of thecorresponding aperture in the compartment sidewall.

3. A grid as in claim 1 wherein said element holder includes a plateportion engaging the compartment sidewall and wherein the projectingportion of said element holder includes two curved clamps projectingtoward the center of the respective compartment.

1. A SUPPORTING GRID FOR SUPPORTING A PLURALITY OF ELEMENTS ENGAGED IN AHEAT EXCHANGE PROCESS AGAINST SIDEWAYS SHIFTING COMPRISING: A PLURALITYOF GRID STRIPS CONNECTED TOGETHER TO FORM THE SIDEWALLS OF A PLURALITYOF COMPARTMENTS HAVING PARALLEL AXES; A PLATE SPRING EXTENDINGLONGITUDINALLY IN EACH COMPARTMENT, SAID PLATE SPRING HAVING ACONTINUOUS SURFACE FACING THE SIDEWALL OF THE RESPECTIVE COMPARTMENT,SAID SPRING HAVING A CENTRAL ARCH-LIKE BEND PROJECTING TOWARD THECENTRAL OF THE RESPECTIVE COMPARTMENT FOR ENGAGING AN ELEMENT THEREINAND HAVING AT EACH END OF THE ARCH-LIKE BEND A SMALLER BEND FACING THEOPPOSITE DIRECTION, SAID SPRING FURTHER HAVING STRAIGHT END PORTIONSWHICH ENGAGE THE SIDEWALL OF THE RESPECTIVE SIDEWALL, EACH PORTIONEXTENDING LONGITUDINALLY OUTWARDLY FROM THE RESPECTIVE SMALLER BEND SOTHAT THE SURFACE OF THE END PORTION ENGAGING THE SEDEWALL IS PART OFSAID CONTINUOUS SURFACE, EACH OF SAID SMALLER BENDS PROJECTING THROUGHAN APERTURE IN THE ADJACENT SIDEWALL AND ENGAGING ONLY THAT EDGE OF THERESPECTIVE APERTURE WHICH IS ADJACENT THE STRAIGHT END PORTIONS OF THEPLATE SPRING TO THEREBY FASTEN SAID PLATE SPRING TO SAID ADJACENTSIDEWALL; AND AN ELEMENT HOLDER IN EACH COMPARTMENT ENGAGING THESIDEWALL OPPOSITE THE RESPECTIVE PLATE SPRING AND HAVING A PORTIONPROJECTING TOWARD THE CENTER OF THE COMPARTMENT FOR ENGAGING AN ELEMENTTHEREIN ON THE OPPOSITE SIDE FROM THE RESPECTIVE PLATE SPRING.
 2. A gridas in claim 1 wherein said element holder includes a plate portionengaging the compartment sidewall, said plate portion being providedwith two apertures each of which coincides with one of said apertures inthe compartment sidewall, an edge of each aperture in the plate portionbeing bent into a lip which grasps the edge of the correspondingaperture in the compartment sidewall.
 3. A grid as in claim 1 whereinsaid element holder includes a plate portion engaging the compartmentsidewall and wherein the projecting portion of said element holderincludes two curved clamps projecting toward the center of therespective compartment.